Configuration and controlling method of boost circuit having pulse-width modulation limiting controller

ABSTRACT

The proposed boost circuit includes a DC/DC converter having a switch, receiving an input voltage and outputting an input voltage feedback signal, an output voltage feedback signal, an input current feedback signal and an output voltage after a boost of the input voltage, and a feedback control circuit having a pulse-width modulation limiting controller, coupled to the converter, receiving the input voltage feedback signal, the output voltage feedback signal and the input current feedback signal and generating an output signal with a fixed time period. The output signal is employed to control the switching of the switch so as to generate the boost.

FIELD OF THE INVENTION

The present invention relates to a boost circuit and its controllingmethod. More specifically, this invention relates to a boost circuitwith a pulse-width modulation limiting controller (PWMLC) and thecontrolling method thereof.

BACKGROUND OF THE INVENTION

Please refer to FIG. 1, which is the schematic circuit diagram of aconventional boost circuit 1 in the prior art. In FIG. 1, the boostcircuit includes a DC/DC boost converter 11 and a feedback controlcircuit 12. The feedback control circuit 12 further includes avoltage/current detector 121 for receiving an input voltage feedbacksignal S_(Vi), an output voltage feedback signal S_(Vo) and an inputcurrent feedback signal S_(Ii) generated by the DC/DC boost converter11, an oscillator 122, a modulator 123, a soft-starting unit 124 and afeedback controller 125. In which, an input voltage V_(in) turns into anoutput voltage V_(o) after a boost, and the output voltage V_(o) iscontrolled by an output signal K of the feedback controller 125. Asshown in FIG. 2, the variations of the output voltage V_(o) of the boostcircuit 1 is increasing from an initial value S to a peak value Pgradually and then decreasing to a stable value Vo slowly. Theoperational principles of the boost circuit 1 are described as follows.The voltage/current detector 121 coverts the detected signal into avoltage signal and outputs the voltage signal to the modulator 123firstly. The modulator 123 modulates the time period of a pulse trainaccording to the voltage signal and a first output signal generated bythe oscillator 122 secondly. The modulated pulse train is outputted fromthe modulator 123 to the feedback controller 125 and compared with thefirst output signal generated by the oscillator 122 and a second outputsignal generated by the soft starting unit 124 thirdly. And the outputsignal K is generated and outputted by the feedback controller 125 tocontrol the switching of a switch Q1 of the boost circuit 1 so as togenerate the boost lastly.

According to the waveform of the output voltage V_(o) as shown in FIG.2, the value of the output voltage V_(o) is rising from an initial valueS to a peak value P and then decreasing from P to a stable value Vo.Since the conventional boost circuit 1 will make the output voltageV_(o) rise to the highest value of P, relatively the electronic elementsof the boost circuit 1 such as the switch Q1, the diode D and the outputcapacitor C1 must have the higher withstand voltage and the higherreliability, and the manufacturing costs of these electronic elementsare higher. The power consumption of the conventional boost circuit 1 isrelatively higher and more expensive since the output voltage V_(o) willraise to the peak value P, which is higher than the rated voltage Vo.

Keeping the drawbacks of the prior arts in mind, and employingexperiments and research full-heartily and persistently, the applicantfinally conceived the configuration and the controlling method of aboost circuit having a pulse-width modulation limiting controller.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to propose a boostcircuit having a PWMLC and the controlling method thereof to avoid theoutput voltage of the boost circuit from raising to a peak value, whichis higher than the rated voltage, so as to lower down the powerconsumptions and the total manufacturing costs of the boost circuit.

According to the first aspect of the present invention, the boostcircuit includes a DC/DC converter having a switch, receiving an inputvoltage and outputting an input voltage feedback signal, an outputvoltage feedback signal, an input current feedback signal and an outputvoltage after a boost of the input voltage, and a feedback controlcircuit having a PWMLC, coupled to the converter, receiving the inputvoltage feedback signal, the output voltage feedback signal and theinput current feedback signal and generating an output signal with afixed time period through a control of the PWMLC for controlling a turnon and a turn off of the switch so as to generate the boost.

Preferably, the output signal is a pulse train, and the pulse train hasa first pulse amplitude while the output voltage is increasing from aninitial value to a stable value and a second pulse amplitude after theoutput voltage reaches the stable value.

Preferably, the second pulse amplitude is larger than the first pulseamplitude.

Preferably, the control circuit further includes a voltage/currentdetector coupled to the converter and the PWMLC, receiving the inputvoltage feedback signal, the output voltage feedback signal and theinput current feedback signal and generating a voltage output signal, anoscillator generating a saw-tooth wave, a modulator coupled to thevoltage/current detector, the PWMLC and the oscillator, receiving thevoltage output signal and the saw-tooth wave and generating a modulatedsignal, a soft starting unit coupled to the PWMLC and generating a softstarting control signal, and a feedback controller coupled to theoscillator, the modulator and the soft starting unit, receiving thesaw-tooth wave, the modulated signal and the soft starting controlsignal and generating the output signal.

Preferably, the PWMLC outputs a first, a second and a third controlsignals to the voltage/current detector, the modulator and the softstarting unit respectively so as to control at least one of thevoltage/current detector, the modulator and the soft starting unit forgenerating the output signal.

Preferably, the first control signal is a first voltage clamping signalfor outputting a first voltage with a first fixed value from thevoltage/current detector, the second control signal is a period limitedsignal for allowing the modulated signal to have a fixed period, and thethird control signal is a second voltage clamping signal for outputtinga second voltage with a second fixed value from the soft starting unit.

Preferably, the PWMLC further includes a circuit starter starting thePWMLC and outputting a starting signal, a first voltage clamper coupledto the circuit starter and the voltage/current detector, receiving thestarting signal and outputting the first control signal, a time periodlimiter coupled to the first voltage clamper and the modulator,receiving the starting signal and outputting the second control signal,and a second voltage clamper coupled to the time period limiter and thesoft starting unit, receiving the starting signal and outputting thethird control signal.

Preferably, the modulator is a pulse-width modulator.

Preferably, the feedback controller is a NAND gate.

Preferably, the converter is one of a DC/DC boost converter and a DC/DCbuck-boost converter.

Preferably, the feedback control circuit has an output terminal and theswitch is a MOSFET having a gate coupled to the output terminal of thefeedback control circuit.

According to the second aspect of the present invention, the method forcontrolling a boost circuit, in which the boost circuit includes a DC/DCconverter having a switch and a feedback control circuit having a PWMLC,a voltage/current detector, an oscillator, a modulator, a soft startingunit and a feedback controller, includes the steps of: (a) transmittingan input voltage feedback signal, an output voltage feedback signal andan input current feedback signal from the converter to thevoltage/current detector; (b) transmitting a first, a second and a thirdcontrol signals generated by the PWMLC to the voltage/current detector,the modulator and the soft starting unit respectively so as to controlat least one of the voltage/current detector, the modulator and the softstarting unit; (c) transmitting a voltage output signal generated by thevoltage/current detector to the modulator; (d) transmitting a saw-toothwave generated by the oscillator to the modulator and the feedbackcontroller; (e) transmitting a modulated signal generated by themodulator and a soft starting control signal generated by the softstarting unit to the feedback controller; (f) transmitting an outputsignal having a fixed period generated by the feedback controller to theconverter; and (g) controlling a turn on and a turn off of the switchthrough the output signal to increase an output voltage from an initialvalue to a stable value so as to generate a boost.

Preferably, the first control signal is a first voltage clamping signalfor outputting a first voltage with a first fixed value from thevoltage/current detector, the second control signal is a period limitedsignal for allowing the modulated signal to have a fixed period, and thethird control signal is a second voltage clamping signal for outputtinga second voltage with a second fixed value from the soft starting unit.

Preferably, the method for controlling a boost circuit further includesthe steps of: (h) starting the PWMLC and outputting a starting signal;(i) receiving the starting signal and outputting the first controlsignal; (j) receiving the starting signal and outputting the secondcontrol signal; and (k) receiving the starting signal and outputting thethird control signal.

Preferably, the output signal is a pulse train, and the pulse train hasa first pulse amplitude while the output voltage is increasing from ainitial value to a stable value and a second pulse amplitude after theoutput voltage reaches the stable value.

Preferably, the second pulse amplitude is larger than the first pulseamplitude.

The present invention may best be understood through the followingdescriptions with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the schematic circuit diagram of a conventional boost circuitin the prior art;

FIG. 2 shows the waveforms of the output voltage V_(o) and thecorresponding output signal K of the feedback controller versus time ofthe conventional boost circuit of FIG. 1 respectively, in which theoutput voltage V_(o) is increasing from an initial value S to a peakvalue P and then decreasing to a stable value Vo;

FIG. 3( a) is the schematic circuit diagram of the first preferredembodiment of the boost circuit having a PWMLC and a boost converter ofthe present invention;

FIG. 3( b) is the schematic circuit diagram of the second preferredembodiment of the boost circuit having a PWMLC and a buck-boostconverter of the present invention;

FIG. 4 shows the waveforms of the output voltage V_(o) and thecorresponding output signal K of the feedback controller versus time ofthe first preferred embodiment of the proposed boost circuit of FIG. 3(a) respectively, in which the output voltage V_(o) is increasing from aninitial value S to a stable value Vo; and

FIG. 5 shows the block diagram of the PWMLC of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer to FIG. 3( a), it shows the schematic circuit diagram ofthe first preferred embodiment of the boost circuit 2 of the presentinvention. In which, the boost circuit 2 includes a DC/DC boostconverter 21 for receiving an input voltage V_(in) and outputting anoutput voltage V_(o) after a boost of the input voltage V_(in) and afeedback control circuit 22. The feedback control circuit 22 furtherincludes a voltage/current detector 221, a PWMLC 222, an oscillator 223,a modulator 224, a soft starting unit 225 and a feedback controller 226.The feedback control circuit 22 is coupled to the DC/DC boost converter21 for receiving an input voltage feedback signal S_(Vi), an outputvoltage feedback signal S_(Vo) and an input current feedback signalS_(Ii) generated by the DC/DC boost converter 21 and generating anoutput signal K with a fixed period T (as shown in FIG. 4) through acontrol of the PWMLC 222. In which, the PWMLC 222 respectively outputs afirst control signal S_(C1), a second control signal S_(C2) and a thirdcontrol signal S_(C3) to the voltage/current detector 221, the modulator224 and the soft starting unit 225 to control at least one of thevoltage/current detector 221, the modulator 224 and the soft startingunit 225 so as to generate the output signal K. The switching of aswitch Q1, which could be a MOSFET, of the DC/DC boost converter 21 iscontrolled by the output signal K so as to generate the boost of theinput voltage V_(in). Besides, the voltage/current detector 221 iscoupled to the DC/DC boost converter 21 and the PWMLC 222 for receivingthe input voltage feedback signal S_(Vi), the output voltage feedbacksignal S_(Vo) and the input current feedback signal S11 and generating avoltage output signal S_(O), and the oscillator 223 is employed togenerate a saw-tooth wave. The modulator 224 is coupled to thevoltage/current detector 221, the PWMLC 222 and the oscillator 223 forgenerating a modulated signal S_(M). The soft starting unit 225 iscoupled to the PWMLC 222 and generates a soft starting control signal,which is a pulse train. The feedback controller 226 is coupled to theoscillator 223, the modulator 224 and the soft starting unit 225 forgenerating the output signal K. Furthermore, the feedback controller 226is a NAND, the modulator 224 is a pulse-width modulator, and the outputsignal K is a pulse train preferably. During the time period that theoutput voltage V_(o) is raising from the initial value S to the stablevalue Vo, the pulse train of the output signal K has the first pulseamplitude W1. After the output voltage V_(o) reaches the stable valueVo, the boost circuit 2 is under a normal operation, and the pulse trainof the output signal K has the second pulse amplitude W2. The secondpulse amplitude W2 is larger than the first pulse amplitude W1 due to aload of the boost circuit 2. The aforementioned first control signalS_(C1) is a first voltage clamping signal and employed to make thevoltage/current detector 221 output a first voltage having a first fixedvalue, the aforementioned second control signal S_(C2) is a periodlimiting signal and employed to make modulated signal SM generated bythe modulator 224 have a fixed period, and the aforementioned thirdcontrol signal S_(C3) is a second voltage clamping signal and employedto make the soft starting unit 225 output a second voltage having asecond fixed value.

FIG. 3( b) is the schematic circuit diagram of the second preferredembodiment of the boost circuit 3 of the present invention. In which,the boost circuit 3 includes a DC/DC buck-boost converter 31 forreceiving an input voltage V_(in) and outputting an output voltage V_(o)after a boost of the input voltage V_(in) and a feedback control circuit32. The feedback control circuit 32 further includes a voltage/currentdetector 321, a PWMLC 322, an oscillator 323, a modulator 324, a softstarting unit 325 and a feedback controller 326. The feedback controlcircuit 32 is coupled to the DC/DC buck-boost converter 31 for receivingan input voltage feedback signal S_(Vi), an output voltage feedbacksignal S_(Vo) and an input current feedback signal S_(Ii) generated bythe DC/DC buck-boost converter 31 and generating an output signal K witha fixed period T (as shown in FIG. 4) through a control of the PWMLC322. In which, the switching of a switch Q1 of the DC/DC buck-boostconverter 31 is controlled by the output signal K so as to generate theboost of the input voltage V_(in). The differences between the secondpreferred embodiment of the boost circuit 3 of the present invention andthe first preferred embodiment of the boost circuit 2 of the presentinvention are that the second preferred embodiment of the boost circuit3 of the present invention includes a DC/DC buck-boost converter 31, andthe first preferred embodiment of the boost circuit 2 of the presentinvention includes a DC/DC boost converter 21, both of the first and thesecond preferred embodiments of the boost circuit 2/3 of the presentinvention could boost the input voltage V_(in) and output an outputvoltage V_(o), and the rest of the operational principles and theconfigurations of the first and the second preferred embodiments of thepresent invention 2/3 are exactly the same.

Since both of the first and the second preferred embodiments of theboost circuit 2/3 of the present invention have the PWMLC 222/322 asabove-mentioned (see FIGS. 3( a) and 3(b) respectively), the PWMLC 222of the first preferred embodiment of the boost circuit 2 is employed asan example and elaborated as follows. Please refer to FIG. 5, which isthe block diagram of the PWMLC 222 of the first preferred embodiment ofthe boost circuit 2 of the present invention. In which, the PWMLC 222includes a circuit starter 2221 for starting the PWMLC 222 andoutputting a starting signal Str, a first voltage clamper 2222 coupledto the circuit starter 2221 and the voltage/current detector 221 forreceiving the starting signal Str and outputting the first controlsignal S_(C1), a time period limiter 2223 coupled to the first voltageclamper 2222 and the modulator 224 for receiving the starting signal Strand outputting the second control signal S_(C2), and a second voltageclamper 2224 coupled to the time period limiter 2223 and the softstarting unit 225 for receiving the starting signal Str and outputtingthe third control signal S_(C3). The first and the second preferredembodiments of the boost circuit 2/3 of the present invention commonlyshare the same operational principles (see FIGS. 3( a) and 3(b)), andthe controlling method of the boost circuit 2 of the first preferredembodiment of the present invention is further elaborated as an exampleas follows. The proposed method for controlling a boost circuit, inwhich the boost circuit 2 includes a DC/DC converter 21 having a switchQ1 and a feedback control circuit 22 having a PWMLC 222, avoltage/current detector 221, an oscillator 223, a modulator 224, a softstarting unit 225 and a feedback controller 226, includes the steps of:(a) transmitting an input voltage feedback signal S_(Vi), an outputvoltage feedback signal S_(Vo) and an input current feedback signalS_(Ii) from the DC/DC boost converter 21 to the voltage/current detector221; (b) transmitting a first, a second and a third control signalsS_(C1), S_(C2) and S_(C1) generated by the PWMLC 222 to thevoltage/current detector 221, the modulator 224 and the soft startingunit 225 respectively so as to control at least one of thevoltage/current detector 221, the modulator 224 and the soft startingunit 225; (c) transmitting a voltage output signal S_(O) generated bythe voltage/current detector 221 to the modulator 224; (d) transmittinga saw-tooth wave generated by the oscillator 223 to the modulator 224and the feedback controller 226; (e) transmitting a modulated signalS_(M) generated by the modulator 224 and a soft starting control signalgenerated by the soft starting unit to the feedback controller 226; (f)transmitting an output signal K having a fixed period T generated by thefeedback controller 226 to the DC/DC converter 21; and (g) controlling aturn on and a turn off of the switch Q1 through the output signal K toincrease an output voltage V_(o) from an initial value S to a stablevalue Vo so as to generate a boost.

According to the aforementioned descriptions, the proposed boost circuithaving a PWMLC and the controlling method thereof are provided to avoidthe output voltage V_(o) of the boost circuit from raising to a peakvalue P, which is higher than the rated voltage Vo, so as to lower downthe power consumptions and the total manufacturing costs of the boostcircuit.

While the invention has been described in terms of what are presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention need not be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims, which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures. Therefore, the above description and illustration should notbe taken as limiting the scope of the present invention which is definedby the appended claims.

1. A boost circuit, comprising: a DC/DC converter having a switch,receiving an input voltage and outputting an input voltage feedbacksignal, an output voltage feedback signal, an input current feedbacksignal and an output voltage after a boost of said input voltage; and afeedback control circuit coupled to said converter and comprising: apulse-width modulation limiting controller (PWMLC) outputting a first, asecond and a third control signals; a voltage/current detector coupledto said converter and said PWMLC, receiving said input voltage feedbacksignal, said output voltage feedback signal, said first control signaland said input current feedback signal, and generating a voltage outputsignal; a modulator coupled to said voltage/current detector and saidPWMLC, receiving said voltage output signal and said second controlsignal and generating a modulated signal; an oscillator generating andoutputting a saw-tooth wave to said modulator; a soft starting unitreceiving said third control signal and generating a soft startingcontrol signal; and a feedback controller coupled to said oscillator,said modulator and said soft starting unit, receiving said saw-toothwave, said modulated signal and said soft starting control signal andgenerating an output signal; wherein said feedback controller generatessaid output signal with a fixed time period through a control of saidPWMLC to control at least one of said voltage/current detector, saidmodulator and said soft starting unit for controlling a turn on and aturn off of said switch so as to generate said boost.
 2. The circuitaccording to claim 1, wherein said output signal is a pulse train, andsaid pulse train has a first pulse amplitude while said output voltageis increasing from an initial value to a stable value and a second pulseamplitude after said output voltage reaches said stable value.
 3. Thecircuit according to claim 2, wherein said second pulse amplitude islarger than said first pulse amplitude.
 4. The circuit according toclaim 1, wherein said first control signal is a first voltage clampingsignal for outputting a first voltage with a first fixed value from saidvoltage/current detector, said second control signal is a period limitedsignal for allowing said modulated signal to have a fixed period, andsaid third control signal is a second voltage clamping signal foroutputting a second voltage with a second fixed value from said softstarting unit.
 5. The circuit according to claim 1, wherein said PWMLCfurther comprises: a circuit starter starting said PWMLC and outputtinga starting signal; a first voltage clamper coupled to said circuitstarter and said voltage/current detector, receiving said startingsignal and outputting said first control signal; a time period limitercoupled to said first voltage clamper and said modulator, receiving saidstarting signal and outputting said second control signal; and a secondvoltage clamper coupled to said time period limiter and said softstarting unit, receiving said starting signal and outputting said thirdcontrol signal.
 6. The circuit according to claim 1, wherein saidmodulator is a pulse-width modulator.
 7. The circuit according to claim1, wherein said feedback controller is a NAND gate.
 8. The circuitaccording to claim 1, wherein said converter is one of a DC/DC boostconverter and a DC/DC buck-boost converter.
 9. The circuit according toclaim 1, wherein said feedback control circuit has an output terminaland said switch is a MOSFET having a gate coupled to said outputterminal of said feedback control circuit.
 10. A method for controllinga boost circuit, wherein said boost circuit comprises a DC/DC converterhaving a switch and a feedback control circuit having a pulse-widthmodulation limiting controller (PWMLC), a voltage/current detector, anoscillator, a modulator, a soft starting unit and a feedback controller,comprising the steps of: (a) transmitting an input voltage feedbacksignal, an output voltage feedback signal and an input current feedbacksignal from said converter to said voltage/current detector; (b)transmitting a first, a second and a third control signals generated bysaid PWMLC to said voltage/current detector, said modulator and saidsoft starting unit respectively so as to control at least one of saidvoltage/current detector, said modulator and said soft starting unit;(c) transmitting a voltage output signal generated by saidvoltage/current detector to said modulator; (d) transmitting a saw-toothwave generated by said oscillator to said modulator and said feedbackcontroller; (e) transmitting a modulated signal generated by saidmodulator and a soft starting control signal generated by said softstarting unit to said feedback controller; (f) transmitting an outputsignal having a fixed period generated by said feedback controller tosaid converter; and (g) controlling a turn on and a turn off of saidswitch through said output signal to increase an output voltage from aninitial value to a stable value so as to generate a boost.
 11. Themethod according to claim 10, wherein said first control signal is afirst voltage clamping signal for outputting a first voltage with afirst fixed value from said voltage/current detector, said secondcontrol signal is a period limited signal for allowing said modulatedsignal to have a fixed period, and said third control signal is a secondvoltage clamping signal for outputting a second voltage with a secondfixed value from said soft starting unit.
 12. The method according toclaim 10, further comprising the steps of: (h) starting said PWMLC andoutputting a starting signal; (i) receiving said starting signal andoutputting said first control signal; (j) receiving said starting signaland outputting said second control signal; and (k) receiving saidstarting signal and outputting said third control signal.
 13. The methodaccording to claim 10, wherein said output signal is a pulse train, andsaid pulse train has a first pulse amplitude while said output voltageis increasing from a initial value to a stable value and a second pulseamplitude after said output voltage reaches said stable value.
 14. Themethod according to claim 13, wherein said second pulse amplitude islarger than said first pulse amplitude.